As a circuit pattern refinement of a semiconductor device is enhanced, inspecting electrical defects and finding out causes of the defects become a more crucial issue. In particular, a defect analysis to cut and fabricate a sample, and analyze the shape and material of the sample is growing in importance for investigating the causes of the defects. An analysis using a transmission electron microscope (referred to as a “TEM”, hereinafter) or a scanning transmission electron microscope (referred to as a “STEM”, hereinafter) is essential in refinement of a circuit pattern at a nanometer level, and such an analysis requires a technique to precisely and accurately prepare a desirable sample for an electron microscopic observation.
An observation sample for a TEM or a STEM is prepared into a thin sample piece having a thickness of approximately 100 nanometers, which allows an electron beam to transmit the sample. A focused ion beam (referred to as “FIB”, hereinafter) fabrication device is used for producing such a thin sample piece. The FIB fabrication device focuses an ion beam into a fine spot, so as to fabricate the sample through an electrostatic deflection scanning.
The prepared thin sample piece through the FIB fabrication has a damaged layer on its surface. The damaged layer is formed such by ions entering the inside of the sample, and converting a crystal structure into an amorphous structure thereof. The damaged layer is also produced in an interface between different materials. This damaged layer deteriorates transmitting performance of the electron beam relative to the sample when a TEM or a STEM is used. Such deterioration hinders a clear electron beam image, resulting in difficulty in observation. Therefore, fabrication is required to remove a damaged layer if a thin sample piece is produced through the FIB fabrication. An inert gas ion beam with low acceleration is used to remove the damage layer.
However, since the thickness of the damage layer is approximately several nanometers, an engineer is required to have a high manipulation technique to remove the damaged layer.